> Is physics "hate speech"

If it's somehow an incitement to an immediate illegal action then it may be. Otherwise it's not.

In the US, hate speech isn't like being offended, it's not in the eye of the beholder. It's been covered a number of times by the Supreme Court.

And China is quite different from the US wrt free speech. US courts take a very dim view of restrictions to political free speech. It's quite a stretch to say the same about China. In fact, I'd argue that there are plenty of Western democracies who are less lenient in that regard than the US.